This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. The goal is to determine the structures of components of the budding-yeast inner kinetochore, with the longer-term objective of creating a complete picture of kinetochore molecular organization. In the case of budding yeast, the components of the inner kinetochore -- that is, the proteins directly or very closely associated with centromeric DNA -- include centromere-binding factors 1 and 3 (Cbf1 and CBF3), Mif2, a "specialized" nucleosome in which H3 is replaced by a centromere-specific histone known as Cse4 (CENP-A in humans), and a nucleosome assembly factor, Scm3. During 2009, we determined the structure of Ndc10, a major component of CBF3. During 2010, we have determined structures of assembly states of the Cse4 nucleosome: a three-way complex of Cse4, H4, and a fragment of Scm3 (at 2.3 [unreadable] resolution) and a Cse4:H4 heterotetramer (at 2.6 [unreadable] resolution). The two structures contribute to our growing understanding of pathways of kinetochore assembly.